Constitutive Modeling of Nonlinear Rheological Behavior of Carbon Nanotube-Filled Polypropylene Nanocomposites

Abstract

Abstract The rheological behavior of multi-walled carbon nanotube (MWCNT)-filled polypropylene (PP) nanocomposites with different filler loadings was experimentally studied and simulated using constitutive modeling. Rheological behavior was characterized in small amplitude oscillatory shear (SAOS) flow, large amplitude oscillatory shear (LAOS) flow, startup of shear flow, steady shear flow, and stress relaxation after the imposition of a step shear strain. Virgin PP and PP with CNT loadings of 1, 3, and 5 wt% were used. The formation of a rheological percolation network was observed at these loadings. The Leonov and Simhambhatla-Leonov models were used to simulate the rheological behavior. In the linear region, the simulations provided good predictions of the experimental data for both the unfilled and filled PP. In the nonlinear region, the simulations also provided good results for the virgin PP and satisfactory results for the PP/1 wt%CNT nanocomposite under most flow conditions. However, for the other two nanocomposites the model showed mixed results.